Phonon-Polaritons in Nanoscale Waveguides

TL;DR

This paper explores how phonon-polaritons, formed by strong photon-phonon coupling via stimulated Brillouin scattering, influence optical transparency and opacity in nanoscale waveguides, revealing spectral features like peaks and dips.

Contribution

It introduces the concept of phonon-polaritons in nanoscale waveguides and analyzes their spectral signatures using the input-output formalism.

Findings

Phonon-polaritons cause two peaks in linear waveguide spectra.

In ring waveguides, they produce two dips in transmission spectra.

Spectral features indicate transparency and opacity gaps.

Abstract

We investigate the phenomena of Brillouin induced opacity in nanoscale linear waveguides and Brillouin induced transparency in nanoscale ring waveguides. The concept of phonon-polariton is required in order to get a deep understanding of such phenomena. Phonon-polaritons are coherent superposition of photons and phonons obtained in the strong coupling regime induced through stimulated Brillouin scattering in the presence of a pump field. The formation of phonon-polaritons can be observed via linear optical spectra that are calculated here using the input-output formalism. For a linear waveguide the signature of phonon-polaritons appears as two peaks in the transmission spectrum with an opacity gap, and for a ring waveguide as two dips in the transmission spectrum with a transparency gap.